Saadé N E, Barchini J, Tchachaghian S, Chamaa F, Jabbur S J, Song Z, Meyerson B A, Linderoth B
Department of Anatomy, Cell Biology and Physiology, American University of Beirut, Riad El Solh Beirut, Beirut, 1107-2020, Lebanon,
Exp Brain Res. 2015 Apr;233(4):1041-52. doi: 10.1007/s00221-014-4180-x. Epub 2014 Dec 24.
Activation of the dorsal columns is relayed to supraspinal centers, involved in pain modulation, probably via the descending fibers in the dorsolateral funiculi (DLF). The present study examines the role of the DLF in the attenuation of pain-related signs by spinal cord stimulation (SCS). Several groups of rats were subjected to nerve injury and to chronic bilateral DLF lesions at C5-7 level. In each animal, two sets of miniature electrodes were implanted, a caudal system placed in the dorsal epidural space at low thoracic level and another implanted over the dorsal column nuclei, rostral to the lesions. Stimulation (50 Hz, 0.2 ms; 70 % of motor threshold) was applied for 5 min via either of the electrodes. Behavioral tests were used to assess the effects of SCS on the nerve injury-induced mechanical and cold hypersensitivity and heat hyperalgesia. Prior to application of SCS, antagonists to either of GABAA or B, 5-HT1 or 1-2 or α/β-adrenergic receptors were injected i.p. Both stimulations produced comparable decreases (80-90 % of the control) of neuropathic manifestations in rats with intact spinal cords. DLF lesions attenuated the effects of both types of stimulation by about 50 %. Pretreatment with receptor antagonists differentially counteracted the effects of rostral and caudal stimulation; the inhibition with rostral stimulation generally being more prominently influenced. These results provide further support to the notion of important involvement of brainstem pain modulating centers in the effects of SCS. A major component of the inhibitory spinal-supraspinal-spinal loop is mediated by fibers running in the DLF.
背柱的激活可能通过背外侧索（DLF）中的下行纤维传递至上脊髓中枢，参与疼痛调节。本研究探讨了DLF在脊髓刺激（SCS）减轻疼痛相关体征中的作用。几组大鼠接受神经损伤并在C5 - 7水平进行慢性双侧DLF损伤。在每只动物中，植入两组微型电极，一组尾侧系统置于胸段低位的硬脊膜外间隙，另一组植入损伤部位头侧的背柱核上方。通过任一电极施加刺激（50 Hz，0.2 ms；运动阈值的70%），持续5分钟。行为测试用于评估SCS对神经损伤诱导的机械性和冷超敏反应以及热痛觉过敏的影响。在施加SCS之前，腹腔注射GABAA或B、5 - HT1或1 - 2或α/β - 肾上腺素能受体的拮抗剂。两种刺激在脊髓完整的大鼠中均使神经病理性表现产生类似程度的降低（对照组的80 - 90%）。DLF损伤使两种刺激的效果减弱约50%。用受体拮抗剂预处理可不同程度地抵消头侧和尾侧刺激的效果；对头侧刺激的抑制作用通常受到更显著的影响。这些结果进一步支持了脑干疼痛调节中枢在SCS效应中起重要作用的观点。抑制性脊髓 - 上脊髓 - 脊髓环路的一个主要组成部分由DLF中的纤维介导。
